From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751956AbdKFKVX (ORCPT ); Mon, 6 Nov 2017 05:21:23 -0500 Received: from mx1.redhat.com ([209.132.183.28]:44824 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751675AbdKFKVV (ORCPT ); Mon, 6 Nov 2017 05:21:21 -0500 DMARC-Filter: OpenDMARC Filter v1.3.2 mx1.redhat.com 5C623BDF7 Authentication-Results: ext-mx05.extmail.prod.ext.phx2.redhat.com; dmarc=none (p=none dis=none) header.from=redhat.com Authentication-Results: ext-mx05.extmail.prod.ext.phx2.redhat.com; spf=fail smtp.mailfrom=pbonzini@redhat.com Subject: Re: [PATCH] KVM: X86: Fix softlockup when get the current kvmclock timestamp To: Wanpeng Li Cc: "linux-kernel@vger.kernel.org" , kvm , =?UTF-8?B?UmFkaW0gS3LEjW3DocWZ?= , Wanpeng Li References: <1509929721-3027-1-git-send-email-wanpeng.li@hotmail.com> <5b0d3e0b-141f-b18b-d74a-bc56265d34df@redhat.com> From: Paolo Bonzini Message-ID: Date: Mon, 6 Nov 2017 11:21:09 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.4.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.29]); Mon, 06 Nov 2017 10:21:21 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 06/11/2017 11:06, Wanpeng Li wrote: > 2017-11-06 17:29 GMT+08:00 Paolo Bonzini : >> On 06/11/2017 01:55, Wanpeng Li wrote: >>> This can be reproduced when running kvm-unit-tests/hyperv_stimer.flat and >>> cpu-hotplug stress simultaneously. kvm_get_time_scale() takes too long which >>> results in softlockup. >> >> Apart from the pr_debug, kvm_get_time_scale should take less than a >> microsecond. The patch is fine, but can you confirm that pr_debug is >> the culprit? > > I can still encounter softlockup after removing the pr_debug. Is kvm_get_time_scale getting into an infinite loop then? That would be the actual bug. Paolo